Synthesis and Characterization of Isoxazole-Based Energetic Plasticizer Candidates EEIN and IDN

Article abstract of DOI:10.1002/ejoc.201801285

This study presents the synthesis of ethyl 5-[(nitrooxy)methyl]isoxazole-3-carboxylate (EEIN) and isoxazole-3,5-diylbis(methylene) dinitrate (IDN). These compounds, each derived from 5-(hydroxymethyl)isoxazole-3-carboxylate, were fully characterized and their explosive sensitivity properties were determined. EEIN was isolated as a solid material with a relatively low melting temperature and IDN was isolated as a liquid with excellent energetic performance properties. In addition, we report the molecular structure of ethyl 5-[(nitrooxy)methyl]isoxazole-3-carboxylate as determined by single-crystal X-ray diffractometry. These compounds possess promising properties as plasticizing ingredients in propellant formulations.

Full text of DOI:10.1002/ejoc.201801285

A Journal of
Accepted Article
Title: Synthesis and Characterization of Isoxazole-Based Energetic
Plasticizer Candidates EEIN and IDN
Authors: Pablo E Guzman, Rosario C Sausa, Leah A Wingard, Rose A
Pesce-Rodriguez, and Jesse J Sabatini
This manuscript has been accepted after peer review and appears as an
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of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
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content of this Accepted Article.
To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201801285
Link to VoR: http://dx.doi.org/10.1002/ejoc.201801285
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10.1002/ejoc.201801285
European Journal of Organic Chemistry
COMMUNICATION
Synthesis and Characterization of Isoxazole-Based Energetic
Plasticizer Candidates EEIN and IDN
Pablo E. Guzmán,* [a] Rosario C. Sausa,[b] Leah A. Wingard,[a] Rose A. Pesce-Rodriguez[b] and Jesse J.
Sabatini [a]
This manuscript is dedicated to the memory of Dr. Brad E. Forch, a world-class friend, colleague and mentor.
Abstract: This study presents the synthesis of ethyl 5-
((nitrooxy)methyl) isoxazole-3-carboxylate (EEIN) and isoxazole-3,5-
diylbis(methylene) dinitrate (IDN). These compounds, each derived
balance, low volatility, improved long-term stability and facile
synthetic sequences are critical for incorporation into high-
performance systems.
from
5-(hydroxymethyl)isoxazole-3-carboxylate,
were
fully
characterized and explosive sensitivity properties were determined.
EEIN was isolated as a solid material with a relatively low melting
temperature and IDN was isolated as a liquid with excellent energetic
performance properties. In addition, we report the molecular structure
of ethyl 5-((nitrooxy)methyl) isoxazole-3-carboxylate as determined
by single crystal x-ray diffractometry. These compounds possess
promising properties as plasticizing ingredients in propellant
formulations.
ONO2
ONO2
NO
ONO2
O2
NO
O2
Nitroglycerine
(NG)
Ethyleneglycol dinitrate
(EGDN)
= 3.5 %
ΩCO2
Ω
Ω
Ω
CO = 24.7 %
= 50 °C
= 0 %
= 21 %
CO2 T = 114 C°CO
Tdec
NO
dec
ONO2
O2
O
O
NO
O2
ONO2
Introduction
ONO2
Trimethylolethane trinitrate
(TMETN)
Triethyleneglycol dintitrate
(TEGDN)
The development of new energetic plasticizers remains an
active area of research within the energetic materials community.1
Nitroglycerin (NG), a legacy propellant/plasticizing ingredient, has
seen widespread use in military and civilian applications. These
include solid propellant formulations used in guns, rockets, air
launched tactical motors, powering missiles, explosives, ground-
launched interceptors and space boosters. Unfortunately, NG is
sensitive to spark, has a low tolerance to friction and begins to
decompose at 50 °C.2 Despite sensitivity and decomposition
concerns, NG continues to serve as a commonly used energetic
ingredient.
Ω
Ω
Ω
Ω
CO2 = -34.5 %
= -3.1 %
CO2 = -66 %
= -26 %
= 158 C°CO
T
= 228C°OC
Tdec
dec
Figure 1. Selected examples of common energetic plasticizers (Tdec
decomposition temperature).
=
Since its discovery in 1888 by Claisen,3 the isoxazole core has
seen prolific use across several areas of chemical and biological
research.
Pharmaceuticals,4
natural
products,5
and
Examples of premier energetic plasticizers are shown in
Figure 1. Common features include alkyl nitrate esters and
ethereal functional groups. These compounds have been
designed and synthesized primarily to mitigate safety concerns
associated with NG. However, nitrate ester-containing
compounds often require chemical stabilizers due to their
propensity to undergo autocatalytic decomposition which
consequently leads to costly surveillance programs. Thus, the
discovery of discrete molecules possessing low sensitivities, high
density, improved formulation profiles, acceptable oxygen
agrochemicals6 have examples containing the isoxazole core.
However, in the context of energetic materials (EMs), these
structural motifs have been less prominent. Recently, our
laboratory disclosed the synthesis of nitrate ester-functionalized
bi-isoxazolebis (methyl nitrate) (BIDN) and bi-isoxazoletetrakis
(methyl nitrate) (BITN).7,8 Entry to the 3,3' system was realized
via an efficient metal-free double 1,3-dipolar cycloaddition.
Focusing our efforts towards the formation of 3,5-disubstituted
mono-isoxazoles, we employ a base-catalyzed cycloaddition
reaction to access two new potential energetic plasticizing
ingredients. Herein, we report ethyl 5-((nitrooxy)methyl)
isoxazole-3-carboxylate
diylbis(methylene) dinitrate (IDN, 4).
(EEIN,
2)
and
isoxazole-3,5-
[a]
Dr. P. E. Guzmán, Dr. L. A. Wingard, Dr. J. J. Sabatini
U. S. Army Research Laboratory
Energetic Technology Branch
Aberdeen Proving Ground, MD 21005, U.S.A.
E-mail: pablo.e.guzman2.civ@mail.mil
https://www.arl.army.mil/www/default.cfm
Dr. R. C. Sausa, Dr. R. A. Pesce-Rodriguez
U. S. Army Research Laboratory
Results and Discussion
[b]
The synthesis of 2 and 4 was accomplished through a well-
established DMAP-catalyzed 1,3-dipolar cycloaddition between
propargyl alcohol and ethyl nitroacetate.9 This approach afforded
cycloadduct 1 in 95 % yield (Scheme 1, eq. 1). Direct exposure of
Energetic Material Science Branch
Aberdeen Proving Ground, MD 21005, U.S.A.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/ejoc.201801285
European Journal of Organic Chemistry
COMMUNICATION
1 to 100 % HNO3 furnished energetic isoxazole 2 in 88 % yield
(Scheme 1, eq. 2).10 Exposure of 1 to lithium aluminum hydride
(LAH) provided isoxazole diol 3 in 37 % isolated yield (Scheme 1,
eq. 3).11,12 In the presence of 100 % HNO3, diol 3 was converted
to isoxazole dinitrate 4, in 92 % yield (Scheme 1, eq. 4).
According to differential scanning calorimetry (DSC)
measurements, compound 2 melts at 35 °C followed by
decomposition at 160 °C.18 The density was determined by gas
pycnometry to be 1.406 g/cm3.
Table 2. Physical and thermodynamic properties of compounds 2 and 4.
1)
2)
OH
O
N
O
DMAP (10 mol %)
OH
EtO
NO2
EtOH, 78 o
C, 72 h
2
4
NG
14
TMETN
-
EtO
O
O
1, 95 %
Tm[°C][a]
35
-
OH
ONO2
O
N
N
Tdec [°C][b]
160
164
50
158
EtO
EtO
100 % HNO3,
0 o
ΩCO2 [%][c]
ΩCO [%][d]
ρ [gcm-3][e]
PCJ [GPa][f]
Vdet [ms-1][g]
-88.82
-37.01
1.406
11.248
5958
-512
-40.16
-3.65
1.494
22.047
6943
-45.8
3.5
-34.5
-3.1
O
O
C, 2 h
1
EEIN, 2, 88 %
24.7
1.6
OH
OH
3)
4)
O
N
N
LAH
O
N
OH
EtO
HO
1.488
23.7
7050
-442
HO
THF, 0 o
C, 1 h
O
1
3, 37 %
25.3
7700
-370
O
O
N
ONO2
O2NO
100 % HNO3,
0 o
C, 2 h
ΔfH° [kJ/
3
IDN, 4, 92 %
mol–1][h]]
Scheme 1. Synthetic sequence for 2 and 4.
Isp[s][i]
168.4
238.9
243.8
247.2
[a] onset temperature of melting [b] onset decomposition temperature [c]
CO2 oxygen balance [d] CO oxygen balance [e] experimental density
determined by gas pycnometry for compound 2. [f] predicted detonation
pressure, [g] predicted detonation velocity [h] predicted molar enthalpy of
Sensitivity data were determined experimentally and the
results are displayed in Table 1.13, 14 Compounds 2 and 4 show
impact sensitivities of >37 J and 29.4 J, both of which are
considerably lower than RDX (6.2 J). Thus, according to the UN
recommendations on the transport of dangerous goods
compound 2 is to be classified as insensitive and dinitrate 4 as
less sensitive.15 The friction sensitivity is >352 N for compound 2
and 176 N for compound 4, both of which are better than RDX
and NG. The sensitivity to spark for 2 was identical to RDX and
decreases significantly to 3.125 J for dinitrate 4.16 For practical
use as energetic plasticizers, the benchmark sensitivities are
defined to be not higher than that of NG. Thus, the sensitivities of
these new materials are in a useful range.
formation, [i] specific impulse (chamber pressure
equilibrium).
= 68 atm (frozen
Isoxazole dinitrate 4 is a liquid material which melts at -76 °C
and has a decomposition temperature of 164 °C which is higher
than TMETN (158 °C) and significantly higher than NG (50 °C). A
density of 1.494 g/cm3 was experimentally determined. The onset
decomposition temperature and density values for IDN is greater
than TMETN (Table 2, entries 2 and 5). The detonation velocities
of 2 (5958 m/s) and 4 (6943 m/s) were calculated and 4 is
comparable to TMETN (7050 m/s).
Table 1. Sensitivity properties of 2 and 4.
Single crystal x-ray diffraction data and their analysis verified
the structure of 2. The details of the data acquisition and structure
solution and refinement are provided in the supplementary
material.19-21 Compound 2 crystallizes with two independent
molecules in the asymmetric unit (2A and 2B, see Fig. 2).
Impact [J][a]
Spark [J][b]
Friction
[N][c]
2
4
>37
0.125
3.125
>352
176
29.4
NG
6
0.0062
0.125
92
RDX
6.2
156
[a] Impact sensitivity, h50 value [b] spark sensitivity, [c] friction sensitivity
Calculated explosive performances and experimentally
determined physical properties are provided in Table 2.17
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10.1002/ejoc.201801285
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COMMUNICATION
Figure 3. Superimposition of structure 2B (green) onto structure 2A (red).
Figure 2. Molecular conformation and atom-numbering schemes of compounds
2, comprising of two distinct molecules (2A and 2B) in its asymmetric unit. Non-
hydrogen atoms are shown as 50 % probability displacement ellipsoids.
Each molecule consists of three nearly planar moieties: an
isoxazole ring [C/C2/C3/O1/N1; r.m.s. deviation = 0.0014 (1) (2A)
and 0.0015 (1)
Å (2B)], an alkyl ester nitrate group
[C4/O2/N2/O3/O4, r.m.s. deviation = 0.0031 (2A) and 0.006 (1) Å
(2B)], and a carboxylate ester group [C5/O5/O6/C6/C7; r.m.s.
deviation = 0.023 (1) Å (2A) and 0.029 (2) Å (2B)]. The latter
moiety is the least planar with the largest deviation resulting from
the C6A/C6B atoms (distances of C6A/C6B atoms to respective
plane = 0.037 and -0.047 Å). In each molecule, the carboxylate
ester and alkyl ester nitrate groups adopt respectively equatorial
and axial positions with respect to the rings. The carboxylate ester
planes subtend respective dihedral angles of 4.3 (1) o and 6.6 (1)
o for 2A and 2B with respect to the isoxazole ring planes, whereas
the alkyl ester nitrate planes subtend respective dihedral angles
of 88.4 (1) o (2A) and 89.8 (1) o (2B) in relation to the ring planes.
The nitrate group planes of the two molecules are nearly normal
to each other [dihedral angle = 81.3 (1)o] and exhibit a plane
centroid-to-plane centroid distance of 3.779 (2) Å. Intra- and
intermolecular interactions play a key role in the crystal packing
of molecules. In compound 2, O∙∙∙H contacts govern the
intramolecular interactions in both molecules. Specifically, in
molecule 2A the O4A atoms form bifurcated contacts with the
H4AA and H4AB atoms [contact distance = 2.470 (3) Å and 2.537
(4) Å, respectively], whereas the O5A atoms form contacts with
the H6AA and H6AB atoms [contact distance = 2.648 (2) and
Figure 4. Crystal packing of 2 viewed along the a axis. Dashed lines represent
both intramolecular and intermolecular interactions.
Compound 2 crystalizes in the triclinic P-1 space group with
four molecules in its unit cell. Figure 4 reveals its molecular
stacking along the a axis. The isoxazole rings link sideways
(centroid-to-centroid distance = 5.6517 (1) Å), forming nearly
planar sheets [centroid-to-centroid distance = 3.640 (2) Å] almost
parallel to (010).
Table 3. Crystal data for 2.
Molecular
formula[a]
C7H8N2O6
216.16
2.731 (2) Å, respectively].
Molecule 2B exhibits similar
interactions and contact distances as those of molecule 2A. Van
der Waals contacts between the O atoms and H atoms of adjacent
molecules [O3A∙∙ H6BAi = 2.648 (3) Å and O5A∙∙∙H2Aii = 2.622 (4)
Å; symmetry codes: (i) 1-x, 1-y, 1- z and (ii) -1+x, -y, 2-z] play a
key role in the intermolecular interactions in both molecules. Also
noteworthy are the interactions between the O atoms and N
atoms of adjacent molecules [O4A∙∙∙N2Biii = 2.713 (3) Å;
symmetry code: (iii) 2-1, -y, 2-z] and the N atoms and H atoms of
adjacent molecules [N1A∙∙∙H4AAiv = 2.744 (3) Å; symmetry code:
(iv) -1+ x, y, z]. Molecule 2B exhibits similar interactions with
comparable contact distances as 2A.
Formula weight
[g/mol]
Temperature °K
298.0 (1)
Triclinic
Crystal system
Space group
P-1
a/Å
b/Å
c/Å
α/°
β/°
5.6517(4)
12.9580(9)
14.0580(8)
106.546(5)
91.758(5)
Both molecules have nearly identical bond lengths, bond
angles, and torsion angles, consistent with those reported for
other isoxazole-based molecules.22-26. A superimposition of the
two structures yields a r.m.s. deviation of 0.051 Å (see Fig. 3).
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10.1002/ejoc.201801285
European Journal of Organic Chemistry
COMMUNICATION
followed by heating. Flash column chromatography was performed on
silica gel 60Å (230-400 mesh). Impact sensitivity testing was performed
using a modified Picatinny Arsenal drophammer, and friction sensitivity
was performed with a BAM friction apparatus in accordance with NATO
STANAG guidelines. Spark sensitivity testing was performed with a Firing
Test System Model 931 machine. X-ray diffraction (XRD) studies were
performed with a SuperNova Dualflex diffractometer containing an EosS2
charge-couple device detector and a molybdenum Mo-Kα (λ = 0.71073 Å)
radiation source. Ethyl 5-(hydroxymethyl)isoxazole-3-carboxylate (1) was
prepared according to published literature procedures.9
γ/°
91.300(6)
Volume/Å3
985.91(12)
4
Z
Based on the molecular mass and lattice constants listed in
Table 3, we obtain a density of 1.456 g/cc at 298 °K, in agreement
with the value measured by gas pycnometry at room temperature
(see Table 2).
CCDC 1858640 (for 2) contains the supplementary crystallographic data
for this manuscript. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre.
Conclusions
Ethyl 5-((nitrooxy)methyl)isoxazole-3-carboxylate: To a round-bottom
flask was added 100 % nitric acid (21 mL) and cooled to 0 °C. Once cool,
ethyl 5-(hydroxymethyl)isoxazole-3-carboxylate (1.50g, 8.76 mmol, 1.00
equiv) was added at a rate such that the internal temperature never
exceeded 10 °C. The reaction was allowed to stir for 2 hours. The reaction
was quenched by pouring into ice-water. The mixture was transferred to a
separation funnel and the organic product was extracted with DCM (3 x
150 mL). The organic layers were combined, carefully washed with
saturated aqueous NaHCO3, dried over MgSO4, filtered and concentrated
under reduced pressure to provide pure yellow liquid product which
solidifies upon cooling (1.66 g, 88 % yield). 1H NMR (400 MHz; d6-DMSO)
δ 7.13 (s, 1H), 5.86 (s, 2H), 4.37 (q, J = 8 Hz, 2H), 1.32 (t, J = 4 Hz, 3H);
13C NMR (100 MHz, D6-DMSO) δ 166.4, 158.9, 156.4, 106.3, 64.1, 62.1,
13.9; IR (neat): 3124, 1726, 1650, 1277.
In summary, two new 3,5-disubstituted isoxazole-based energetic
ingredients, EEIN and IDN, were developed using well-
established and reliable chemical methods. For these two
compounds, their energetic behavior was determined. Both
materials exhibited acceptable to excellent insensitivity towards
electrical and mechanical stimuli. The calculated detonation
parameters are in a useful range for EEIN and IDN is comparable
in performance to NG and TMETN. These compounds show great
promise as plasticizing ingredients in military and civilian
applications as they contain i) non-bonding electrons capable of
interacting with electrophilic binders and ii) alkyl nitrate linkages
which provide needed miscibility with commonly used energetic
plasticizers. Moreover, these compounds can serve as
complimentary ingredients to previously published bi-isoxazole
compounds. Exploring the potential of these resulting novel
molecules is underway in our laboratory.
Isoxazole-3,5-diyldimethanol: To a 250 mL round-bottom flask was
added ethyl 5-(hydroxymethyl)isoxazole-3-carboxylate (4.06 g, 23.7 mmol,
1.00 equiv) and anhydrous THF (100 mL). The solution was cooled to 0 °C.
Once cool, lithium aluminum hydride (1.98 g, 52.3 mmol, 2.20 equiv.) was
carefully added. The reaction was allowed to stir for 1 h. The reaction was
stopped by addition of Et2O (40 mL) followed by slow addition of water (2
mL) and 15% aqueous NaOH (2 mL). Water (6 mL) was added and the
reaction was allowed to warm to room. MgSO4 was added and stirred for
15 minutes. The crude product was filtered through a glass frit and
thoroughly rinsed with EtOAc and concentrated under reduced pressure.
The crude material was purified by flash chromatography (95:5
DCM/MeOH) on silica gel to afford the pure product as a yellow liquid (1.14
g, 37 %). Rf = 0.2 (90:10 DCM:MeOH); 1H NMR (400 MHz; d6-DMSO) δ
6.32 (s, 1H), 5.59 (t, J = 8 Hz, 1H), 5.42 (t, J = 8 Hz, 1H), 4.54 (d, J = 4 Hz,
2H), 4.48 (d, J = 8 Hz, 2H); 13C NMR (100 MHz, d6-DMSO) δ 172.5, 164.1,
100.7, 54.8, 54.6; IR (neat): 3315, 2926, 2872, 1036.
Experimental Section
Note: We did not experience any issues in handling and synthesizing the
materials described in this article. Nonetheless, they should be handled
with extreme care, implementing standard safety procedures for handling
energetic materials.
Experiments requiring anhydrous conditions were conducted under an
atmosphere of dry nitrogen using flame-dried glassware. Solvents were
dried by a Grubbs-type solvent purification system or purchased from
commercial sources and used where appropriate. Unless otherwise noted,
all other reagents were obtained from commercial sources and used as
received. 1H Nuclear Magnetic Resonance (NMR) spectra were recorded
at 400 MHz. Data is presented as follows: chemical shift (in ppm on the δ
scale relative to δH 7.26 for the residual protons in CDCl3 or δH 2.50 for
the residual protons in d6-DMSO), multiplicity (s = singlet, d = doublet, t =
triplet, q = quartet, m = multiplet, br = broad), coupling constant (J/Hz),
integration. Coupling constants were taken directly from the spectra and
are uncorrected. 13C NMR spectra were recorded at 100 MHz, and all
chemical shift values are reported in ppm on the δ scale, with an internal
reference of δC 77.0 for CDCl3 or δC 39.52 for d6-DMSO. Melting points
and decomposition temperatures were measured on a TA instruments
DSC Q2000 at a heating ramp rate of 5 °C/min. Infrared spectral data was
measured on a ThermoFisher Nicolet iS50 FTIR instrument. Analytical
TLC was performed on glass-backed silica gel F254 plates (EMD
Chemicals). Visualization of developed plates was performed by
fluorescence quenching or by staining with aqueous potassium
permanganate (KMnO4) or phosphomolybdic acid (PMA) in ethanol stain
Isoxazole-3,5-diylbis(methylene) dinitrate: To a round-bottom flask was
added 100 % nitric acid (23 mL) and cooled to 0 °C. Once cool, isoxazole-
3,5-diyldimethanol (1.12g, 8.69 mmol, 1.00 equiv) was added at a rate
such that the internal temperature never exceeded 10 °C. The reaction
was allowed to stir for 2 hours. The reaction was quenched by pouring into
ice-water. The mixture was transferred to a separation funnel and the
organic product was extracted with DCM (3 x 75 mL). The organic layers
were combined, carefully washed with saturated aqueous NaHCO3, dried
over MgSO4, filtered and concentrated under reduced pressure to provide
pure yellow liquid product (1.75 g, 92 % yield). 1H NMR (400 MHz; d6-
DMSO) δ 6.88 (s, 1H), 5.81 (s, 2H), 5.74 (s, 2H); 13C NMR (400 MHz, d6-
DMSO) δ 165.1, 157.9, 105.5, 65.6, 64.3; IR (neat): 3144, 2913, 1632,
1272, 834.
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10.1002/ejoc.201801285
European Journal of Organic Chemistry
COMMUNICATION
[12] Conditions employing DIBAL and NaBH4 were explored. However, no
improvements were observed.
Acknowledgements
[13] NATO Standardization Agreement (STANAG) on Explosives, Impact
Sensitivity Tests, no. 4489, 1st ed., September 17, 1999.
We are indebted to the U.S. Army for funding this work. The
authors thank, Ms. Lauren B. Blaudeau, Mr. Eric Johnson and Dr.
Chase A. Munson for technical assistance and Dr. Edward F. C.
Byrd for predicted performance values. P.E.G thanks Drs. Clayton
P. Owens (BAE Systems, Inc.), David E. Chavez (Los Alamos
National Laboratory) and Gregory W. Drake (AMRDEC) for
helpful discussions.
[14] NATO Standardization Agreement (STANAG) on Explosive, Friction
Sensitivity Tests, no. 4487, 1st ed., August 22, 2002.
[15] a) Test methods according to the UN Manual of Tests and Criteria,
Recommendations on the Transport of Dangerous Goods, United Nations
Publication, New York, Geneva, 4th revised ed., 2003: Impact: insensitive >40
J, less sensitive _35 J, sensitive _4 J, very sensitive _3 J; friction: insensitive
>360 N, less sensitive: 360 N, sensitive <360 N and >80 N, very sensitive _ 80
N, extremely sensitive _ 10 N; b) www.reichel-partner. de.
Keywords: cycloaddition • energetic materials • nitrate ester •
[16] a). Precautionary measures must be taken when handling energetic
materials as the human body can generate up to 0.025 J of static energy. b)
NATO Standardization Agreement (STANAG) on Explosives, Electrostatic
Discharge Sensitivity Tests, no. 4490, 1st ed., Feb 19, 2001; b)
http://www.ozm.cz/en/sensitivity-tests/esd-2008a-small-scale-
electrostaticspark-sensitivity-test/.
propellant •synthesis design
[1]
For a recent example of efforts directed towards the development of new
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Mater. 2016, 34, 129-137.
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[18] Liquid and crystalline samples of 2 (EEIN) were individually analysed by
DSC. Both samples were cooled to -50 °C and slowly heated. Melting and
decomposition temperatures were nearly identical for both samples, however,
a cold crystallization onset temperature was observed at -26 °C for liquid EEIN.
See supplemental information for thermal data.
[5]
a) G. Stork, A. A. Hagedorn III, J. Am. Chem. Soc. 1978, 100, 3609-3611;
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[10] It is important to note that compound 2 is isolated as a liquid which
solidifies upon cooling. See supplemental information for thermal profile.
[11] Crude yields of 53 % were observed. See supplemental information for
workup and isolation details.
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10.1002/ejoc.201801285
European Journal of Organic Chemistry
COMMUNICATION
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COMMUNICATION
The synthesis and characterization
of two new energetic materials is
described. These isoxazole-based
molecules show promise as
plasticizing ingredients in propellant
formulations.
Key Topic*
Guzmán,* Pablo, E., Sausa, Rosario,
C., Wingard, Leah, A., Pesce-
Rodriguez, Rose, A., Sabatini,
Jesse, J.
ONO2
O
N
O
ONO2
N
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NO
O2
Title
O
EEIN
IDN
Synthesis and Characterization of Isoxazole-Based
Energetic Plasticizer Candidates EEIN and IDN
*Energetic Isoxazoles
Layout 2:
COMMUNICATION
Key Topic*
Author(s), Corresponding Author(s)*
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final letter height should not be less than 2 mm.))
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Title
Text for Table of Contents
*one or two words that highlight the emphasis of the paper or the field of the study
This article is protected by copyright. All rights reserved.